Ok firstly yay first post and secondly i spent hours trying to install BT4 on my ibm netvista p3 it only has a cd reader and it doesnt have the option to boot from USB in the bios settings but after searching the web and forums i found that this worked for me.
Download software called PLoP boot manager you can get it from here:http://download.plop.at/files/bootmngr/plpbt-5.0.10.zip once you downloaded the .zip file open it up and burn the plpbt.iso to a cd
Grab a 2gb or larger USB drive and install BT4 to it you can do that by downloading this software: UNetbootin - Homepage and Downloads and then selecting your ISO of BT4 in the browse box next to diskimage and make sure that the diskimage thing is selected then choose your USB drive and hit ok this will take a while for it to install.
after you have installed BT4 to your USB you can then go and place your disk you burned earlier (the one with PLoP) and boot off of it and you should see a menu to choose where you want the computer to boot from next make sure your USB is in the computer and then select USB and wait a second and then you will be greeted by a box asking you how you would like to run BT4 just boot into the most appropriate option for you (if you are having trouble and its saying that you need to select another video mode you can simply restart the computer and repeat the process but this time hit tab on how you want to run BT4 and then find where it says vga=....... and change it to video=myfb and then hit enter and wait for it to load)
once in it should show the desktop just remember that it will be slow because you are running off of a USB anyway click the install icon on the desktop and follow the prompts that appear and thats it you should have successfully installed BT4 off a USB.